1. Field of the Invention
The present invention relates to a filter device, and in particular to a filter device which is utilized with computer disk drive systems.
2. Description of the Prior Art
Magnetic disk drives which are used in high numbers throughout the computer industry require a clean environment to operate. Contaminants can lead to corrosion and other problems with the components. It has been found that even ambient levels of urban pollution can lead to corrosion which will also lead to failure of the disk drives. To overcome these problems, the systems may be equipped with filter devices which remove particles and corrosive and condensable vaporous contaminants from the system air. Filter devices utilized include breathers, recirculation filters and static pouches.
Hard disk files normally need to be vented to the atmosphere of the surrounding environment to prevent excess pressure building up in the head disk enclosure. During operation, files will heat up and air will flow out of the head disk enclosure. The thermal cycling of the assembly will result in air flow in and out of the enclosure. Organic vapors condense on the surface of the disk causing the head to stick to the surface of the disk (stiction). The new thin film technology utilized in the higher density disks and the high strength to weight metals utilized in the disk file assembly are very susceptible to corrosion as well. Chemical or adsorptive breathers have been developed to provide for removal of the vaporous and gaseous contaminants in addition to removal of particulate contaminants.
As magnetic drives become more and more compact, smaller components are required. Therefore, the size of the filters and especially the thickness of the filters needs to become more and more compact while providing greater protection. The decreased size and the air flow generated by the high speed mechanisms can cause a pressure differential to occur across a breather or recirculation filter. Therefore, it is necessary that the filter device provide adequate flow through the filter to prevent great pressure differential within the drive. If a large pressure difference does develop across a filter, unfiltered leaks will occur within seals, bearings or other moving parts. With recirculation filters, a high differential pressure increases the clean up time of the drive during initial burn in and spin up.
An example of a prior filter device is represented by U.S. Pat. No. 4,657,570 showing an Air Filter Device, assigned to Donaldson Company, Inc., the assignee of the present invention. Although the filter device provides filtering of air in magnetic disk drive systems, the activated carbon portion for adsorption of corrosive gases and potential condensates must be cut and the construction is relatively complicated. Therefore, the device has higher manufacturing costs and requires greater assembly time. In addition, the filtering portion needs to be cut, thereby leading to possible contamination of the filtering device during assembly. In the extremely clean conditions which are needed for the filtering devices, cutting of portions of the filter media can cause contamination and quality control problems.
It can be seen then that new and improved filter devices for disk drive systems are needed. Such devices should provide for filtering air and removing gaseous contaminants from contaminating the disk drive system. In addition, filter devices should have a construction which provides for a very narrow profile with adequate clearance in the disk drive system. Such a device should be inexpensive and easy to manufacture without contamination during the assembly process. The present invention addresses these as well as other problems associated with filter devices for disk drive systems.